An edger is an apparatus that is used to cut lengthwise edges on a wood board and it typically includes a pair of saws to cut the lengthwise edges. Numerous edging devices have been developed that optimize the physical size of the edged board. These prior devices typically seek to edge the board in order to obtain the largest board possible, and the problem with these devices as applied to hardwood is that they ignore the rounding rule used to price hardwood lumber. In accordance with one aspect of the present invention, an edging apparatus is provided that makes edging decisions based on the rounding rule of the hardwood lumber industry in the United States.
The rounding rule basically provides that the measurement of all boards shall be rounded to the nearest whole board foot. For example, a board having a measurement of 4.4 board feet would be rounded to four board feet, and 4.6 board feet would be rounded to five board feet. Hardwood boards are cut to standard lengths and thicknesses, but the width of the board may be cut to any random size. Thus, the width of the board is critical in determining the number of board feet in a particular board (A board foot is the equivalent of a board that is 1" thick, 1' wide and 1' long). In view of the rounding rule, an edger that merely maximizes the size of the board is wasteful in a sense. For example, it would be wasteful to edge a board so that it measured 4.4 board feet. It would be preferred to edge the board so that it measured 3.6 board feet. A board that measures 3.6 board feet will be rounded to four board feet, the same as a board measuring 4.4 board feet, and the value of the two boards is the same. But, when the board is cut to 3.6 board feet, as opposed to 4.4 board feet, a greater volume of valuable wood chips are produced. Also, in edging the board to achieve 3.6 board feet, as opposed to 4.4 board feet, it is less likely that the board will be degraded for leaving too much wane or will require a second edging.
The present invention provides an ability to edge a board so as to achieve a desired effect taking into consideration the rounding rule. In accordance with one form of the present invention, an edging apparatus is controlled by an operator and has two saws for edging a wood board that is priced by the whole board width in accordance with the rounding rule under which fractions of a board are rounded up or down. The edging apparatus included a positioning device for positioning and holding the saws, and through a selection apparatus the operator selects initial cut positions for the saws. Input devices generate input data that includes board length and thickness parameters and the initial cut positions. In one embodiment, a keyboard is used to provide the board length and thickness parameters and a position feedback circuit is used to provide data on the initial cut positions. A computer is responsive to the input data for computing the best cut positions for the saws based on the rounding rule. The best cut positions are computed to produce an edged board whose measurement exceeds a whole board foot measurement by a desired fraction of a board foot, and an output device is provided for outputting the computed best cut positions so that the saws may be positioned in accordance therewith.
It will be noted that the present invention provides that the best cut positions are determined so that the edged board exceeds a whole board foot measurement by a desired fraction thereof. In many cases, the desired fraction will be slightly more than 0.5, such as 0.6 board feet, so that the board will always be rounded upwardly. However, in other cases, an operator may not wish to take advantage of the rounding rule. In some cases, saw mills have built up a reputation for measurement generosity. That is, customers may buy from a particular saw mill because he feels that the lumber received from that mill is usually rounded down rather than up. In order to maintain this reputation of generous measurements, an operator may prefer to choose the fraction so that it is more than zero but less than 0.5. For example, he may wish to have each board measure 0.2 board feet over a whole board foot and would thus choose the fraction to be 0.2 board feet. In order to achieve flexibility and accommodate different saw mills, one embodiment of the present invention provides an adjustment means that is operable through the computer to adjust the size of the desired fraction of a board foot. In this manner, an operator may make an intelligent decision as to whether his boards should be cut to a size that will cause their measurements to be rounded up or down.
When the computer is calculating the best cut positions, it must know the board thickness and length. In the past, the length trim decision was usually made independently of the edging decision and the two decisions were usually made in different places by different people. This system made it difficult or impossible to make truly intelligent edging and trim decisions that took into consideration the rounding rule. The present invention solves this problem by providing a length trim marker that marks the board with trim marks indicating where the boards should be trimmed to achieve a desired board length based on board length input data. The length trim markers are positioned in front of the saws and the board is marked before it is edged. In this manner, the length trim and edging decisions may be made at the same time by the same operator prior to edging or trimming. Alternatively, an automatic spray marker which sprays digits designating length may be used as trim markers. This marker indicates digitally the length to which the board is to be trimmed.
In accordance with another aspect of the present invention, the apparatus further includes judgment means associated with the computer for making a judgment as to whether the best cut positions should be further apart or closer together than the initial cut positions in order to achieve the desired fraction of a board foot when the board is edged. The judgment in many cases will be to always choose a best cut position in which the cut positions are spaced closer together than the initial cut positions. In another embodiment, the best cut positions may be chosen to be those that are nearest the initial cut positions that achieve the desired fraction of a board foot. Also, an override is provided so that the operator may override the decision of the judgment means as to whether the best cut positions should be further apart or closer together than the initial cut positions, and a further manual override control is provided so that the operator may manually set the position of the saws independently of either of the computed best cut positions.
In accordance with yet another aspect of the present invention, a further embodiment provides a preview table for receiving boards and lasers forming laser lines representing saw lines on the preview table. Positioning apparatus and controls are provided for moving the lasers and laser lines on the preview table to position the laser lines on the board in desired initial cut positions, and initial cut position data is generated by feedback circuitry corresponding to the initial cut positions selected by the operator using the lasers. Based on the initial cut position data, and the other input data, the best cut positions are calculated and an output signal is generated that corresponds to the best cut positions. A control mechananism is responsive to the output signal to position the saws in such best cut positions. In this manner, the lasers and the saws operate independently, and because of this independent operation, the lasers may be used to select best cut positions for a new board while the previous board is being edged.
In the apparatus utilizing a preview table and a plurality of lasers associated with the preview table, the length trim selection may also be made at or adjacent to the preview table. In accordance with another aspect of the present invention, a plurality of lasers form a plurality of laser trim lines across the preview table to indicate possible standard lengths to which the board may be trimmed, and a plurality of trim markers are aligned with the laser trim lines for selectively marking the boards at positions corresponding to the laser trim lines. In the preferred mode, an infeed table is positioned downstream from the preview table and upstream from the saws. A transfer mechanism transfers the boards from the preview table to the infeed table, and as the boards are transferred, the boards are marked by the trim markers.